Previous studies demonstrated that cloned antigen specific CD4+ T cells treated with an inhibitor of DNA methylation, 5- azacytidine (5-azaC), lost the requirement for antigen and could be activated by autologous HLA-D molecules alone, thus becoming autoreactive. Evidence from murine models suggests that these autoreactive cells could produce an autoimmune disease resembling lupus erythematosus (LE). To test whether autoimmune disease may be caused by inhibiting DNA methylation, we asked whether drugs which cause LE affect T cells like 5-azaC. In preliminary experiments we demonstrated that procainamide, hydralazine and 5-azaC all induced autoreactivity in cloned antigen specific T cells, and inhibited 3H- methyl incorporation into newly synthesized T cell DNA. All 3 drugs also induced expression of the same 5 new proteins as measured by 2D gel analysis. These results suggest that two drugs which induce an autoimmune disease may mimic the effects of 5- azaC by inhibiting DNA methylation, inducing new gene expression and inducing autoreactivity in T cells. We therefore hypothesize that some forms of autoimmunity may be cause by agents which activate certain genes, allowing T cell autoreactivity. The experiments described in this proposal are designed to test this hypothesis by 1) confirming that agents which induce autoimmunity also induce T cell autoreactivity and induce gene expression similar to that observed following 5-azaC treatment, 2) testing whether T cells made autoreactive by these agents are capable of activating B cells and macrophages in such a fashion that tissue damage could result, and 3) testing for expression of these genes in autoimmune disease. These studies may help elucidate the pathogenesis of some forms of autoimmunity.